a library of information on how to mix exotic drinks,they could find little about what happens after thedrinking starts.The person who wants to drink responsible y mustknow the short-term and long-term effects of alcohol onthe body. Those who want to understand the socialcustom of drinking, problem drinking, and alcoholismmust also know these effects.SHORT-TERM EFFECTS. Most people drinkalcoholic beverages to get feelings of pleasure as wellas to relieve tension. No doubt that is the reason for thepopularity of alcohol as a social beverage. Drinking hasbecome such a familiar part of our society that we donot think of alcohol as a drug. However, it is as much adrug as one prescribed in carefully regulated dosages bya physician.Alcohol affects the whole body through the centralnervous systemthe brain. Alcohol does not act directlyon the tongue or legs to cause the familiar signs ofslurred speech and an unsteady gait connected withdrunkenness. Instead, it affects the parts of the brain thatcontrol those parts of the body.Alcohol can act as a stimulant at low doses and as abrain depressant at higher doses. The speed with whichalcohol brings on drunkenness and drunken behaviordepends upon the rate of its absorption into thebloodstream and a person's tolerance for alcohol.Although the body must digest food before it canenter the bloodstream, it does not have to digest alcohol.Alcohol immediately passes directly through the wall ofthe stomach and small intestines into the bloodstream.Then the blood rapidly carries it to the brain.Even the first few sips of an alcoholic beverage maycause changes in mood and behavior. These changesmay be influenced by what the person has learned toexpect from previous drink experiences.Alcohol is metabolized (burned and broken down)in the body at a fairly constant rate. As a person drinksfaster than the alcohol can be burned, the drugaccumulates in the body. That results in higher andhigher levels of alcohol in the blood.BLOOD-ALCOHOLLEVELSANDBEHAVIOR. The first consistent changes in mood andbehavior appear at blood-alcohol levels ofapproximately 0.05 percent; that is, 1 part alcohol to2,000 parts blood. That level would result if a 150-poundperson took two drinks in succession. A blood-alcohollevel of 0.05 percent can affect a persons thought,judgment, and restraint and cause the person to feelcarefree. The person feels a release from many ordinarytensions and inhibitions; in other words, the personloosens up. Most people drink in moderation mainly toachieve this relaxed state.As more alcohol enters the blood, the depressantaction of alcohol involves more functions of the brain.At a level of 0.10 percent (1 part to 1,000), voluntarymotor actions-hand and arm movements, walking, andsometimes speech-become clumsy.A level of 0.20 percent (1 part to 500) measurablyimpairs the controls of the entire motor area of the brainas well as that part of the brain that guides emotionalbehavior. At this stage the person will stagger and maywant to lie down. The person may also become easilyangered, may become boisterous, or may weep. Theperson is drunk.A concentration of 0.30 percent (1 part to 300) dullsthe persons response to stimulus and understandingcontrolled by the deeper areas of the brain. At this levela person may be confused or may lapse into a stupor.Although aware of surrounding sights and sounds, theperson has poor understanding of what he or she sees orhears.With 0.40 to 0.50 percent alcohol in the blood (1part to 250 or 200), the person becomes unconscious andmay go into a coma. Still higher levels of alcohol blockthe center portions of the lower brain that controlbreathing and heartbeat, causing death to occur.This progression of effects is not unique to alcohol.Other hypnotic-sedative drugs, such as barbiturates,ether, and chloral hydrate, can also produce thisprogression of effects.Blood-alcohol levels have important legalimplications. In most states, a person with ablood-alcohol level of 0.05 percent or less is legallypresumed sober and in condition to drive a motorvehicle. However, in some states, a person with a levelof 0.10 percent or 0.08 percent is legally presumedintoxicated or under the influence; in others, the0.15-percent level means legal impairment.CHRONIC HEAVY DRINKING. Drinking largeamounts of alcohol for an extended length of timereduces the brains sensitivity to the alcohol. Therefore,a person must drink greater amounts of alcohol to feelits effects. This change in the sensitivity of the brain iscalled tolerance. Increased tolerance is a symptom of allchronic users of addictive drugs and is believed to be thebasis of addiction or dependence.3-16